Coating technology is rewriting the rules of the game in materials science. From smartphone screens to space telescope lenses, this technology has quietly permeated every aspect of our lives, playing a pivotal role in high-tech fields such as optics and electronics.

The principle of thin film coating

Coating, simply put, is a process of covering a surface with one or multiple thin films. The thickness of these films typically ranges from nanometers to micrometers. Although seemingly insignificant, they can significantly alter the physical, chemical, and optical properties of the substrate. It is akin to dressing the material in a specially tailored "outer garment," endowing it with superior performance characteristics it originally lacked.

The principles of coating involve various physical and chemical processes. Among them, the most common are physical vapor deposition (PVD) and chemical vapor deposition (CVD). Physical vapor deposition is carried out in a vacuum environment, where the coating material is transformed into gaseous atoms or molecules through methods such as heating, evaporation, or sputtering. These gaseous particles then deposit and condense on the surface to form a thin film. Chemical vapor deposition, on the other hand, utilizes gaseous precursor substances that undergo chemical reactions under high temperature, plasma, or catalytic conditions to generate solid thin films on the surface.

The function of coating: improving optical performance

Many items experience significant improvements in optical performance after coating treatment. For example, applying an anti-reflective coating on optical lenses can reduce light reflection on the lens surface and increase light transmittance, enabling us to see objects more clearly. This is because the thickness of the anti-reflective coating is meticulously designed so that the reflected light from the upper and lower surfaces of the coating interferes destructively, thereby reducing the intensity of reflected light.

Similarly, coating a highly reflective film on the laser resonator can enhance the laser's reflectivity, improving laser oscillation and output power. The highly reflective film reflects most of the laser energy back into the resonator cavity, allowing it to continuously oscillate and amplify within the cavity, ultimately producing a high-intensity laser beam.